A rotation sensor using multiple magnetoresistive elements (MREs) has been disclosed in, for example, JP-A-2001-153683 and JP-A-H10-332725. In a rotation sensor disclosed in JP-A-2001-153683, two MRE bridges are symmetrically arranged with respect to a magnetic center of a bias magnetic field. On the other hand, in a rotation sensor disclosed in JP-A-H10-332725, two MREs are arranged adjacent to a gear so that signals outputted from the MREs can have a phase difference, and a rotation direction of the gear is detected based on rising edges of the signals.
In recent years, there has been an increase in demand for small and high accuracy sensors. In particular, as the X-by-wire technologies move forward, a rotation sensor is required to meet exacting requirements such as a small size, a detection range of 360°, and an accuracy of 0.1% FS.